1. Recent Findings on Mechanisms for Noise Induced Hearing Loss
Research has shown that oxidative stress plays an important role in noise-induced cochlear injury. Acoustic overexposure leads to several cochlear physiological responses. An important mechanism behind noise induced hearing loss is overproduction of ROS, reactive oxygen species (“oxidants”). This leads to mitochondrial injury and loss of hair cells and neurons through inflammatory pathways (Kopke et al., 2007).
2. Resent Research on Agents that May Ameliorate Hearing Loss
New and accumulating data regarding the role of oxidative stress and cochlear cell death are providing a rational mechanism-based approach for preventing and treating noise-induced hearing loss with pharmacologic agents. Recent research shows that a number of antioxidant and cell death inhibiting compounds can ameliorate deafness associated with acoustic trauma. Of importance are vitamins A, C, and E as well as magnesium. One of the most promising agents is N-acetylcysteine (NAC). It addresses many of the known mechanisms of cochlear injury due to acoustic trauma, functioning as an antioxidant, mitochondrial protectant, and necrosis and cell death inhibitor (Kopke et al., 2007).
However, it is of outmost importance that these agents are taken before noise trauma and/or immediately after the noise trauma. The positive effects of e.g. NAC or vitamins decrease dramatically after a few hours.
There are several products marketed as “noise pills”, “ear pills” or “hearing protection pills”. One of the most promising is called Auraquell™ , and is a combination of vitamins A, C, E, and magnesium. The four active ingredients in Auraquell™, each have, according to the manufacturer, a distinct mechanism of action. Vitamins A, C, and E are antioxidants, while magnesium acts as a vasodilator and may have the additional beneficial effect of reducing swelling of the auditory nerve by preventing noise-induced calcium influx. Whereas each individual agent has shown only small protective effects with long-term dosing, the Auraquell™ combination may, according to the manufacturer, reduce noise induced hearing loss (NIHL) when initiating treatment 1 hour prior to noise exposure or immediately after noise exposure.
WO 2008/095013 A1 deals with an acoustic dose system comprising a first device configured to measure sound pressure levels directed to an ear drum and a second device configured to convert the sound pressure levels into a sound pressure level dose, where the second device sends a notification signal to a third device if the sound pressure level dose is larger than a threshold value, the third device being e.g. a computer system, an audio playback device or a communication device.
US 2008159547 deals with a method for monitoring and reporting sound pressure level exposure for a user of a first communication device is implemented in one embodiment when the device measures a sound pressure level (SPL) of the surrounding environment. The device stores at least the SPL measurement in a memory, producing an SPL exposure record, and displays a visual representation of the SPL exposure record on a display screen.
US 2008/0118087 A1 deals with a miniature sound level dosimeter that is less expensive and more user-friendly than conventional sound level dosimeters.